It is well known that lenses, and in particular spectacle lenses, comprise an ophthalmic substrate having geometrical features adapted to the wearer.
Some coatings can be added on the ophthalmic substrate to obtain a finished ophthalmic lens. The coatings are for instance an anti-abrasive coating to increase the abrasion resistance of the lens, and/or an anti-reflective coating to decrease the reflection of light and/or an anti-soiling coating applied over the anti-reflective coating.
One known method to manufacture an ophthalmic substrate is described in European patent application EP 2 093 018, in which a single blocking piece is provided for surfacing and edging the ophthalmic substrate.
The blocking piece is made from a plastic material moulded in a single piece and is configured to receive an optical substrate, also named blank.
The blocking piece has a reception zone of the blank which is delimited by a peripheral outline and which has a diameter similar to the diameter of the blank.
The blank is mounted and fixed to the blocking piece, a first face of the blank facing a mounting face of the blocking piece.
The system formed by the blank and the blocking piece is then mounted on a surfacing machine for the surfacing of a second face of the blank, the second face being opposite to the first face.
Next, a step of surfacing of the second face of the blank is carried out.
The system formed by the blocking piece and the blank whose second face is machined is then transferred to an edging machine (for instance a grinder) for the edging of a peripheral edge of the blank, which edge links the first and second faces of the blank.
Next, a step of edging of the edge of the blank is carried out. During, the step of edging, the outline of the single blocking piece is further machined.
A substantial portion of the single blocking piece is removed because the step of edging generally machines the blank from a maximum first diameter, for instance equal to around 70 mm, to a maximum second diameter smaller than the first diameter, for instance 30 mm. The second face and the outline of the blank are thus machined in order to form the ophthalmic lens (or at least the ophthalmic substrate) which is cut and has a shape similar to a shape of the spectacle frame on which the ophthalmic lens is configured to be mounted.
The single blocking piece made from plastic material is thus here a disposable blocking piece.
The invention is directed to a method of manufacturing an ophthalmic lens, comprising a step of surfacing and a step of edging, the method being simple, convenient and economical to carry out.